Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$32.33	3.450%	$33.4454	$33.45	$33.45	$33.40
Purchase #2	$111.56	13.845%	$127.0055	$127.01	$127.00	$127.00
Purchase #3	$110.39	11.386%	$122.959	$122.96	$122.95	$123.00
Purchase #4	$229.73	4.185%	$239.3442	$239.34	$239.35	$239.30
Purchase #5	$50.27	10.714%	$55.6559	$55.66	$55.65	$55.70
Purchase #6	$77.40	5.634%	$81.7607	$81.76	$81.75	$81.80
Purchase #7	$51.68	3.205%	$53.3363	$53.34	$53.35	$53.30
7 purchase totals =	$663.36		$713.5070	$713.52	$713.50	$713.50